U.S. patent number 4,259,982 [Application Number 06/095,721] was granted by the patent office on 1981-04-07 for resistive fluid detecting means.
This patent grant is currently assigned to Honeywell Inc.. Invention is credited to James I. Bartels.
United States Patent |
4,259,982 |
Bartels |
April 7, 1981 |
Resistive fluid detecting means
Abstract
A resistive fluid or boiler water type of detecting system has
been disclosed. A single conductor type of probe having a plurality
of conducting regions that are capable of conducting a
bidirectional electric current in either a full bidirectional mode
or in a unidirectional mode has been disclosed. The single probe
element is capable of three separate and distinct states of
operation. The first state is when there is an absence of current,
the second is when there is a unidirectional portion of the
bidirectional current flowing, and the third state is when the full
bidirectional electric current is allowed to flow. An output device
is responsive to these three states to provide different types or
levels of control.
Inventors: |
Bartels; James I. (Hudson,
WI) |
Assignee: |
Honeywell Inc. (Minneapolis,
MN)
|
Family
ID: |
22253298 |
Appl.
No.: |
06/095,721 |
Filed: |
November 19, 1979 |
Current U.S.
Class: |
137/392; 73/304R;
307/118; 340/620; 361/178 |
Current CPC
Class: |
G01F
23/241 (20130101); F24H 9/2007 (20130101); Y10T
137/7306 (20150401) |
Current International
Class: |
G01F
23/24 (20060101); F24H 9/20 (20060101); B01F
023/24 (); G01F 023/00 () |
Field of
Search: |
;73/34R ;137/392
;307/118 ;361/178 ;340/620 ;417/36,44,45 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Walton; G. L.
Attorney, Agent or Firm: Feldman; Alfred N.
Claims
The embodiments of the invention in which an exclusive property
right is claimed are defined as follows:
1. A resistive fluid detecting means adapted to sense a resistive
fluid level in a container, including: unitary probe means having a
diode action and further having a plurality of conductive regions
all of which are in said container and are submersible in said
resistive fluid with said probe means being adapted to be connected
to a source of bidirectional electric current; a first of said
regions being an impedance capable of conducting said bidirectional
electric current; a second of said regions being an impedance
capable of conducting only a unidirectional portion of said
bidirectional electric current; and said first and said second
regions being connected in electrical series and further connected
in a series electrical circuit with said source of bidirectional
electric current; said resistive fluid detecting means responding
separately to the absence of said current, the presence of said
unidirectional portion of said bidirectional current, and to the
presence of said bidirectional current as an indication of a level
of said fluid in said container.
2. A resistive fluid detecting means as described in claim 1
wherein said first conductive region includes a conductive rod; and
said second conductive region includes a conductive rod and
asymmetric current conducting means; said first and said second
conductive regions being joined in electrical series to form a part
of said series electrical circuit.
3. A resistive fluid detecting means as described in claim 2
wherein said rods are metal rods.
4. A resistive fluid detecting means as described in claim 3
wherein said asymmetric current conducting means is a diode.
5. A resistive fluid detecting means as described in claim 1
wherein said first conductive region includes a conductive rod; and
said second conductive region is composed of a material that is
capable of conducting only a unidirectional portion of said
bidirectional electric current when said second conductive region
is in contact with said resistive fluid in said container.
6. A resistive fluid detecting means as described in claim 5
wherein said conductive rod is a metal rod; and said second
conductive region is a titanium rod with said rods being
mechanically joined and in electrical series.
7. A resistive fluid level control system having a resistive fluid
detecting means adapted to sense a resistive fluid level in a
container and to in turn control said fluid level, including: a
unitary probe means having a diode action and further having a
plurality of conductive regions all of which are in said container
and are submersible in said resistive fluid with said probe means
being adapted to be connected to a source of bidirectional electric
current; a first of said regions being an impedance capable of
conducting said bidirectional electric current; a second of said
regions being an impedance capable of conducting only a
unidirectional portion of said bidirectional electric current; said
first and said second regions being connected in electrical series
and further connected in a series electrical circuit with said
source of bidirectional electric current; and fluid level control
means responsive to the absence of said current, the presence of
said unidirectional portion of said bidirectional current, and the
presence of said bidirectional current to control the level of said
conductive fluid in said container.
8. A resistive fluid level control system as described in claim 7
wherein said first conductive region includes a conductive rod; and
said second conductive region includes a conductive rod and
asymmetric current conducting means; said first and said second
conductive regions being joined in electrical series to form a part
of said series electrical circuit.
9. A resistive fluid level control system as described in claim 8
wherein said rods are metal rods.
10. A resistive fluid level control system as described in claim 9
wherein said asymmetric current conducting means is a diode.
11. A resistive fluid level control system as described in claim 7
wherein said first conductive region includes a conductive rod; and
said second conductive region is composed of a material that is
capable of conducting only a unidirectional portion of said
bidirectional electric current when said second conductive region
is in contact with said resistive fluid in said container.
12. A resistive fluid level control system as described in claim 11
wherein said conductive rod is a metal rod; and said second
conductive region is a titanium rod with said rods being
mechanically joined and in electrical series.
Description
BACKGROUND OF THE INVENTION
Resistive fluid detecting means in the form of probes to sense the
presence or absence of a resistive fluid in a container have been
known for many years. One widely used type of installation that
relies on resistive fluid detecting means are boilers. The presence
or absence of boiler water in a heating plant boiler can be
monitored by a resistive fluid detecting probe. This type of probe
normally relies on the establishment of a single conductive circuit
between the probe and the boiler itself. A resistance measurement
is then converted into a decision as to whether or not the boiler
water is present in the boiler. In some systems, two probes are
used to establish two different levels of water in a boiler,
thereby establishing a differential between the need to add water
to the boiler and the normal content of water within the boiler.
The establishment of the differential is desirable in order to
eliminate the need for cycling a pump or solenoid valve when a
ripple or slight movement of the boiler water level occurs at the
end of a probe.
Boiler water sensing mechanisms also have been developed which
utilize floats to sense the level of boiler water and mechanically
operate switches. This type of mechanism is subject to wear and
boiler water scale contamination, thereby creating a sensing
mechanism which may be more complex and less desirable than a
simple resistive fluid detecting type of probe.
SUMMARY OF THE INVENTION
The present invention utilizes a single probe element or means that
has a plurality of conductive regions that are electrically
connected in series with each other and then connected in a series
circuit with a source of bidirectional electric current. The novel
probe means is capable of detecting three different resistive fluid
levels. By using a single probe means that is cable of detecting
three separate states or levels, it is possible to provide for a
system which is capable of detecting the presence of a conductive
fluid and then establishing a differential between the presence of
the fluid and the maximum level to which the fluid is to be
supplied within a container.
When the present invention is applied to boilers utilized in
heating installations, the probe means is capable of sensing the
presence of water, the presence of water in an intermediate or
differential area, and the further maximum level to which the
boiler water is to be maintained in the boiler. The intermediate or
differential area is used so that ripples in the boiler water do
not inadvertently operate the source of water to the boiler. In
typical boiler installations the water is either supplied by
opening a solenoid operated valve from a pressurized source of
water, or is supplied by energizing a pump which supplies water to
the boiler. It is quite apparent that it is undesirable to be
adding small amounts of water due to a ripple or disturbance in the
water at a probe, and therefore the use of a differential is
desirable.
With the present invention a single series circuit is capable of
supplying the necessary control signal to a fluid level control
means that in turn controls either a pump or a valve to supply
water to the boiler. The present invention relies on the
introduction of a asymmetric current conducting function in the
probe means, and the energization of the probe means by a
bidirectional source of electric current. With this arrangement the
probe is capable of providing three separate and distinct signals
to the fluid level control means. The first signal is the total
absence of any electric current when the fluid level is below the
probe element. When the fluid level rises to contact the probe
element, the probe conducts current in a unidirectional manner due
to the presence of an asymmetric current conducting means in the
probe. As the fluid rises, and contacts the upper portion of the
probe, the unidirectional electric current that is flowing is
changed to a bidirectional type of current. The fluid level control
means detects this change and thereby senses the maximum level to
which the fluid or water is to rise.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a simplified probe
means;
FIG. 2 is a complete resistive fluid level control system, and;
FIG. 3 is a simplified version of a second embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 there is disclosed a schematic or simplified version of
the resistive fluid detecting means generally disclosed at 10 which
is part of a resistive fluid level control system that forms the
overall disclosure of FIG. 1. The resistive fluid detecting means
10 includes a probe means generally disclosed at 11 that is made up
of a plurality of conductive regions. In the disclosure of FIG. 1
the upper conductive region is disclosed at 12, while the lower
conductive region is disclosed at 13. The upper conductive region
12 is any type of electrical impedance, such as a conductive metal
rod. The lower or second conductive region 13 is made up of two
elements. The first element is a conductive metal rod 14 which is
connected at 15 to a diode or asymmetric current conducting means
16. The diode 16 is further connected at 17 to the first or upper
conductive region or rod 12. A non-conductive support member 20 has
been disclosed as mechanically holding the upper conductive region
12 and the lower conductive region 13 together along with the diode
16. The diode 16 could be encapsulated in epoxy or plastic in order
to protect it and add mechanical rigidity to the probe means
11.
It is apparent that the probe means 11 comprises an upper
conductive region and a lower conductive region with those two
regions being electrically connected in series with the
intermediate diode 16 so that the lower conductive region 13
becomes an impedance that is capable of conducting an electric
current only in one direction. The reason for this will become
obvious when the overall system has been disclosed.
The probe means 11 is supported (in any appropriate manner) in a
container 21 that could be a boiler for a heating plant or any
other type of container which contains a resistive fluid 22. The
container 21 is grounded at 23. The container or boiler 21 has an
inlet pipe 24 that is supplied with the resistive fluid 22 under
the influence of a pump or pressurized source that is controlled by
a solenoid valve as would be conventional in any boiler
installation. The resistive fluid level control system is completed
by a conductor 25 that is connected through a load resistor 26 to a
source of bidirectional electric curent 27 which in turn is
grounded at 23. The bidirectional source of electric current 27 can
be considered in the disclosure of FIG. 1 as a conventional source
of alternating current supply at an appropriate voltage. An
amplifier means, detector, and output control device such as a
relay is generally disclosed at 30 with a pair of conductors 31 and
32 connecting the amplifier means 30 across the load resistor 26.
The details of an amplifier means, detector, and output relay
configuration for a pump or solenoid will be disclosed in some
detail in connection with FIG. 2. The amplifier means 30 that has
been disclosed simply is an arrangement that is capable of
responding differently to three different voltage states across the
load resistor 26.
OPERATION OF FIG. 1
In the disclosure of FIG. 1 the resistive fluid 22 is disclosed as
below the end of the lower conductive region 13 and it is quite
apparent that in the state shown that no current flows from the
source 27 through the load resistor 26 and the conductor 25 through
the probe means 11. At this time there is therefore no voltage
appearing across the load resistor 26 and the amplifier means 30
responds accordingly. That is, with no voltage at the input of the
amplifier means 30, the output of the amplifier means 30 recognizes
that the resistive fluid 22 in the container 21 is below the probe
means 11 and fluid is introduced in pipe 24.
As soon as the fluid 22 reaches the bottom conductive region 14 an
electric circuit is completed from the source of potential 27
through the load resistor 26 and the conductor 25 along with the
probe means 11 to the ground 23. Due to the presence of the
asymmetric current conductive means or diode 16 the current that
flows in this series circuit is unidirectional. More specifically,
half wave rectified voltage appears across the load resistor 26.
The amplifier means 30 is designed to recognize the difference
between the total absence of a voltage and a half wave rectified
alternating current. A phantom resistance 33 has been disclosed as
representative of the current path that is established when the
conductive fluid 22 reaches the lower conductive region 13 and the
phantom resistor 33 represents the electric circuit between the
probe means 11 and the ground 23.
As the conductive fluid 22 continues to rise in the container 21
the fluid eventually reaches a level where the conductive fluid 22
comes into direct contact with the upper conductive region 12 and
this resistance is shown as the phantom resistance 34. It is
apparent that at this point that the diode or asymetric current
conducting means 16 is shorted out of the circuit and the current
that flows in the circuit through the load resistance 26 now
generates a full wave alternating current voltage across the
resistance 26. The amplifier means 30 responds to this full wave or
bidirectional voltage which reflects that fact that a bidirectional
electric current is flowing in the series circuit in which the
probe means 11 is connected. The amplifier means 30 responds by
turning "off" the pump or closing the valve that supplies the
conductive fluid or water to the pipe 24.
It will thus be apparent that in the system disclosed in FIG. 1
that three separate and distinct operating states have been
established. The first operating state is one in which no voltage
appears across the load resistance 26. The next state is when a
unidirectional or rectified voltage appears across the load
resistance 26. The final or third state is when a bidirectional
current flows in the resistance 26 thereby providing a
bidirectional voltage to the amplifier means 30. With the present
series circuit involving the probe means 11 and the two conductive
regions 12 and 13 three different operating states are
possible.
The principle of operation which was developed schematically in
FIG. 1 will now be applied to a system that is more representative
of the manner in which the boiler water probe element would be
applied to a boiler and how an amplifier means 30 would be
structured for control purposes. Also, the system operation may be
reversed from that described. For example, a sump pump controller
could be turned "on" at a high level of water, and "off" when the
water is below the probe 11. There are other applications for this
reverse mode of operation.
In FIG. 2 the resistive fluid detecting means 10 is again disclosed
with the elements carrying the same reference numbers as disclosed
in FIG. 1. The boiler 21 is connected to the ground 23 that forms
the ground of an amplifier 30'. The probe means 11 is connected by
the conductor 25 to a terminal 35 within the amplifier means 30'.
The terminal 35 is connected through a sensitivity setting resistor
36 that is connected to a tap 37 of a transformer winding 38.
Transformer winding 38 is the secondary step down side of a
transformer generally disclosed at 40 which has a primary winding
41 connected to a pair of line terminals 42 and 43 which are
connected to a conventional source of bidirectional or alternating
current. The winding 38 is further connected through a diode 44 so
that a rectified control potential is supplied on conductor 45 for
the amplifier means 30'.
Connected between the conductor 45 and the ground 23 is a resistor
46 and a field effect transistor generally disclosed at 47. The
field effect transistor 47 is of a type which requires a negative
potential on a gate 50 for the field effect transistor 47 to cease
conduction. The gate 50 is connected to a capacitor 51 and a
resistor 52 that are both in turn connected to the ground 23. The
gate 50 is further connected through a diode 53 to the terminal 35.
The terminal 35 is further connected through a reverse connected
diode 54 to a normally open relay contact 55 that is mechanically
operated by an armature 56 from a relay coil 57. The relay coil 57
is connected at one of its extremities to the conductor 45 and at
its opposite extremity through a further field effect transistor
generally disclosed at 60. The field effect transistor 60 has a
gate 61, but since the field effect transistor 60 is an insulated
gate type of field effect transistor, the gate 61 requires a
positive driving potential to cause the transistor 60 to
conduct.
The field effect transistor 60 is further connected to the ground
23 to complete a current path through the relay coil 57. The relay
coil 57 is paralleled by a capacitor 62 that acts to stabilize the
relay's operation. The relay armature 56 is connected to further
normally open contacts 63 that acts as an output control to control
a pump or solenoid valve 64 that is in turn connected by a pair of
conductors 65 and 66 to the line potential terminals 42 and 43. The
closing of the contacts 63 energize the pump or solenoid valve 64
to supply fluid to the pipe 24 in the operation of the system.
The circuit of the amplifier means 30' is completed by connecting
the gate 61 of the field effect transistor 60 through a zener diode
70 to parallel combination of a resistor 71 and a capacitor 72 to
the ground 23. The capacitor 72 and the resistor 71 form a time
delay circuit in conjunction with a further diode 73 that is
connected between the resistor 46 and the common conductor 74 that
joins the zener diode 70 to the capacitor 72, the resistor 71, and
the normally open relay contact 55.
OPERATION OF FIG. 2
It is initially assumed that the amplifier means 30' has been just
energized by the application of a bidirectional alternating current
in the form of a conventional 60 hertz voltage to the terminals 42
and 43. At this particular time the resistive fluid or water 22 is
below the end of the conductive region 13. At this time also the
relay coil 57 is deenergized and the relay contacts 63 and 55 are
open, as shown in FIG. 2.
As soon as the voltage is applied to the terminals 42 and 43,
voltage appears across the lower portion of the secondary winding
38 and current flows through the diode 53, the resistor 36, and the
lower portion of the winding 38 to the ground 23. This current is
then drawn through a relatively high resistance 52 and
simultaneously through the capacitor 51 to charge the capacitor 51
with a potential that is negative at the gate 50 of the field
effect transistor 47. At the outset or energization of the
terminals 42 and 43, the field effect transistor 47 has had an
insufficient negative potential at the gate 50 to cause it to be in
an "off" state, and therefore bidirectional current has been
flowing through the field effect transistor 47. This drops
substantially all of the voltage across the resistor 46 and there
is effectively a ground potential on the diode 73 where it joins
the field effect transistor 47. This effectively shorts out the
gate 61 of the insulated gate field effect transistor 60 and
therefore the field effect transistor 60 is in an "off" state.
The capacitor 51 rapidly charges and provides a negative potential
at the gate 50 of the field effect transistor 47 thereby turning
the field effect transistor "off". As soon as the field effect
transistor 47 ceases to conduct, the voltage that appears on
conductor 45 is applied through the resistor 46 and the diode 73 to
charge the capacitor 72. As soon as the capacitor 72 takes on a
sufficient charge to break down the zener diode 70, a positive
potential appears at the gate 61 of the field effect transistor 60
thereby turning the field effect transistor 60 "on". The relay coil
57 then draws sufficient current through the field effect
transistor 60 to cause the armature 56 to close the contacts 63 and
55. The closing of the contacts 63 immediately causes the pump or
valve 64 to supply water or a resistive fluid to the pipe 24. The
closing of the contact 55 through the diode 54 effectively locks
the system into this state by supplying a direct source of
potential through the diode 54 to the capacitor 72 to continue to
supply the positive potential on the gate 61 of the field effect
transistor 60 necessary to keep it in conduction.
The resistive fluid 22 rises in the container or boiler 21 until it
reaches the conductive region 13 where a current path is completed
through the diode element 16. This action effectively takes the
diode 53 and its related components out of control of the field
effect transistor 47. Since the relay contact 55 has closed,
however, the field effect transistor 60 is not altered in its state
of conduction and the relay coil 57 is still energized to hold the
contacts 63 closed.
As the resistive fluid or water 22 rises it eventually reaches the
level where it comes in contact with the conductive region 12. As
soon as the water or resistive fluid 22 reaches the conductive
region 12, the resistive fluid 22 acts as a short to the terminal
35 effectively removing the gating potential from the field effect
transistor 60. With the gating potential removed, a slight time
delay is generated by the discharge of the capacitor 72 through the
resistor 71 to hold the gate 61 sufficiently positive for a few
moments to keep the relay energized to prevent ripples in the
resistive fluid or water 22 from causing the pump to accidentally
turn "on" again.
The time delay created by the discharge of the capacitor 72 through
the resistor 71 passes and the gate 61 of the field effect
transistor 60 is such that the necessary positive gating potential
no longer exists. Under this condition the field effect transistor
60 becomes non-conductive and the relay coil 57 is deenergized
thereby dropping out the contacts 55 and 63. This turns "off" the
pump or valve 64 and opens the holding circuit created through the
contact 55. A slight drop in the water or resistive fluid 22 does
not create a cycling action on the pump or valve 64 as a
differential is created by the upper conductive region of the probe
means 11. When the liquid level 22 drops to a sufficient point to
open the circuit entirely, the operation of the system starts over
again. The differential can be established by the design of the
probe and/or the parameters of the particular amplifier circuit
used.
In FIG. 3 a further version of the probe means has been disclosed.
The boiler or container 21 is again disclosed having a resistive
fluid 22 and a ground 23 along with an inlet pipe 24. A probe means
80 is suspended in an appropriate position within the container or
boiler 21. The probe means 80 has an upper region 81 that is an
impedance capable of carrying a bidirectional electric current. A
second conductive region 82 is disclosed which is mechanically and
electrically joined at 83 to the conductive region 81. In this
embodiment, the conductive region 82 is composed of a material that
is capable of conducting only a unidirectional portion of the
bidirectional electric current that is to be applied to the
conductive region 82. A material which provides this function is
titanium. The reason that the titanium is a material which is
capable of conducting only a unidirectional portion of the
bidirectional current when it is applied to the present structure
will be described after the balance of the system has been
described.
The conductive region 81 is connected by a conductor 84 to an
amplifier and output control means 85 that in turn is connected by
a conductor 86 to a source of bidirectional electric current 90.
The source of bidirectional electric current 90 is energized from a
pair of conventional alternating current lines 91 and 92, and the
bidirectional source of electric current 90 is grounded at 23 to
complete its ability to apply a bidirectional electric current
through the container 21 and the resistive fluid 22 to the probe 80
when the resistive fluid 22 rises to a sufficient level.
In FIG. 3 the source of bidirectional electric current 90 is a
source of very low frequency bidirectional electric current. The
source 90 could be any type of oscillator generating a low
frequency alternating current wave form or any other type of
switched bidirectional current such as a positive and/or negative
wave form of a generally rectangular form. The specific electronics
of the bidirectional electric current source 90 is not material to
the present invention, and it is well known in the art to convert a
conventional 60 hertz alternating current to any other convenient
frequency that is desired.
In order to have the embodiment of FIG. 3 functional, it is
necessary that the probe means 80, and particularly the conductive
region 82 be capable of carrying only a unidirectional portion of
the bidirectional current that is applied when the resistive fluid
22 rises to be in contact with the conductive region 82. It should
be understood that a conductive region 82 made of titanium would
have this characteristic. When the titanium conductive region 82 is
at a positive potential and in contact with water in a boiler water
application, the surface of the titanium changes to titanium
dioxide and becomes an insulator. This means that whenever a
positive potential is applied between the conductor 84 and ground,
that the titanium generates a titanium oxide layer that makes the
conductive region 82 non-conductive for that portion of the applied
bidirectional electric current. When the titanium conductive region
82 is subjected to a negative potential on the conductor 84 with
respect to the ground 23, the titanium oxide which is present on
its surface dissolves in the water and the titanium surface becomes
a normal conductor. As such, the system acts as if the system is
operating in a half wave fashion. The only requirement of the
present system is that the frequency of the bidirectional electric
current that is applied must be low enough so that the formation
and removal of the titanium dioxide layer can be accomplished.
With this understanding it will be noted that as the present system
of FIG. 3 has a fluid level so that the resistive fluid 22 is not
in contact with the probe means, it is obvious that no current
flows in the amplifier means 85 and this causes the amplifier means
85 to energize a pump or source of resistive fluid to add fluid so
that the resistive fluid rises until it becomes in contact with the
region 82. At this time, the low frequency bidirectional electric
current is applied between the conductive region 82 and the
resistive fluid 22. Due to the action previously mentioned, the
conductive region is capable of conducting only a unidirectional
portion of the bidirectional electric current. The unidirectional
current flow through the amplifier means 85 is sensed and the
proper control function is provided. As the fluid 22 rises until it
comes in contact with the conductive region 81, the full
bidirectional electric current flows in conductor 84 and the
amplifier 85 turns "off" the pump or source of fluid to the
container 21. It will thus be noted that the probe means 80
functions in this sytem in a manner that is similar to the probe
means 11 of FIGS. 1 and 2.
The manner in which the probe means 11 or 80 is fabricated is
subject to great variation within the knowledge of anyone skilled
in this art. The particular electronics utilized to implement the
operation of a system utilizing the probe means also can be widely
varied within the skill of those working in the electronics art.
For these reasons, the applicant wishes to be limited in the scope
of the design and application of the present invention solely by
the scope of the appended claims.
* * * * *